<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        //闰年的条件： 除以4为0但是除以100不为0 或 除以400为0
        var year = prompt('请输入年份：');
        //将字符串转为整型
        year = parseInt(year);
        if((year % 4 == 0 && year % 100 !=0) || year % 400 == 0){
            alert(year+'是闰年');
        }else{
            alert(year+'不是闰年');
        }
        
    </script>
</body>
</html>